When working in electrical installations, it is important to monitor the condition of circuits and live parts. The primary check (for safety purposes) reveals the presence or absence of voltage in the work area. For this, a voltage presence indicator is used, which is connected manually by the operator, that is, it is not an element of the electrical installation design.
In what cases it is necessary to use a voltage indicator:
- before starting repair work in the electrical installation;
- before applying portable grounding;
- to determine the area where the accident occurred;
- to identify conductive parts of the electrical installation, which should not have a dangerous potential.
Important: The safety, and even the life of an electrician, depends on the correct use of the voltage indicator!
We'll look at how pointers work. high voltage, types and methods of their application.
Division by type
General principles of operation of UNN (low voltage indicators)
To operate the indicator (regardless of its type), it is necessary to ensure the flow of electric current through the circuit of the device. At the same time, the safety of the operator is in the first place. The two-pole design eliminates the contact of open areas of the body with current-carrying parts. But the single-pole voltage indicator works only when the auxiliary electrode is touched with a finger. Accordingly, the design must necessarily include a current limiting system to a safe value. After lowering the current threshold, the device turns into a low voltage indicator, regardless of the real potential on the current-carrying parts.
equipment requirements
To ensure safety and reliability of operation, such devices must be certified. The requirements of the state standard occupy at least a page of text, we highlight the main ones:
- the insulating shell of the device must withstand voltage exceeding the measuring range;
- a single-pole pointer is made in only one case, thus eliminating the need for two-handed operation;
- at one end of the pointer there is a probe for contact with the checked section of the circuit, at the opposite end there is a contact pad for touching the operator's finger;
- a two-pole voltage indicator should consist of two cases with the same security indicators, connected by a flexible insulated cable 1 meter long;
- the open section of the probe must not exceed the length specified for the selected measuring range;
- the light and (or) sound indicator of the presence of potential must be clearly distinguishable under any measurement conditions.
Security standards are the same for the entire territory Russian Federation. No subject, be it Moscow or any regional center, has the right to soften the requirements for the production or use of such equipment.
Consider the operation of the main types of voltage indicators.
Bipolar design
The high voltage indicator with two measuring contacts works on the principle of fixing the passage of current in a circuit section. An internal circuit compares the potential difference between the measuring point and ground (or neutral). If the response threshold exceeds the set value, the indication is triggered.
The execution may be different, depending on the purpose: only indication, search for a breakdown, measurement of the exact voltage value, setting the range (220 V, 380 V). As an example, the illustration shows the electrical circuit of a device that determines the presence of a phase in the measured area and an approximate voltage threshold.
There are no complex integral elements, so such a pointer is reliable and trouble-free in any operating conditions. If measurements are taken outdoors, in bright light - parallel to the light indicator (in this case, it is an LED element), a sound indicator is added.
When a voltage measurement module is added to the measuring circuit, we get a single-mode multimeter designed for safe high voltage measurement.
This is interesting: An ordinary multimeter can also be used as a high voltage indicator. However, it will take time to be ready (setting the appropriate measurement mode). Yes, and with security, not everything is so smooth: specialized devices undergo rigorous certification.
It is not difficult to use such a device: a passive contact on the connecting wire is applied to the earth (zero) bus of the electrical installation. Then touch the potential measuring point with the measuring contact.
Advantages:
- high measurement accuracy, if necessary, you can expand the functionality;
- the ability to work with high voltage without additional means of protecting the operator;
- operator protection is provided: there is no direct contact with open areas of the body.
Flaws:
- higher cost;
- The meter is quite bulky.
Single pole design
Electric current flows between the phase (measuring point) and the ground loop, which provides the body of a person (operator). Inside the device is a simple electrical circuit consisting of a neon lamp and a resistor. The resistance is selected in such a way that the electric current does not exceed a value that is safe for humans.
At the same time, the current strength must ensure reliable operation of the indicator. For a neon lamp, a few hundredths of a milliamp is enough, so that the circuit works stably.
How to use such a pointer? The device is held in one hand, the finger is placed on the rear contact. After that, the measuring probe is applied to the current-carrying part of the electrical installation. If potential is present, the control lamp lights up.
Interestingly, various "advanced" transistor and LED circuits are not as reliable as simple neon lamp and a graphite resistor. A high percentage of false positives does not allow the use of such a device for professional purposes.
Advantages:
- cheapness of the device;
- efficiency of use;
- the ability to work with one hand.
Flaws:
- low accuracy and reliability;
- no extended functionality;
- potentially dangerous: there is contact of open areas of the body with the measuring part of the device.
Non-contact voltage indicator
With direct access to open contacts electrical wiring or electrical installation, voltage measurement is easy. And how to determine the potential (at least its presence) in hidden wiring?
For this, there are non-contact indicators (not to be confused with current clamps).
Such pointers do not work directly with electric current, but with an electromagnetic field that arises around the conductor. In fact, this is a coreless transformer, or inductor.
The simplest pointers react to an alternating magnetic field. When it is detected, the circuit assembled on triggers is triggered, and voltage is applied to the indicator (LED element). To enhance the detection effect, an audible signal is turned on in parallel.
Of course, there can be no talk of any voltage measurements. Moreover, the presence of an electromagnetic field depends on many factors, including the presence of a ground bus next to the conductor. In other words, a high-quality (according to the requirements of the PUE) laid electrical cable will not be detected by a contactless probe.
Important: You cannot use such a pointer as a hidden wiring detector, the detection distance is 1-2 cm in the open air.
Advantages:
- ease of use: no need to look for open contacts;
- safety: no contact with live parts.
Flaws:
- in reality, the device does not guarantee even 50% of the result.
Based on the principle of operation of such an indicator, the stronger the current in the cable, the higher the probability of detecting the potential. Accordingly, if the appliance is not turned on, its supply cable will not actively form an electromagnetic field around itself. In this case, the potential on the phase wire is present, and the danger of electric shock remains.
Important: If you plan to use such an indicator, anyway, before starting work, you should check the absence of voltage in open areas with a conventional contact device.
Before using any measuring instrument make sure you have a safety compliance certificate.
Related videos
Purpose
1. Voltage indicators are designed to determine the presence or absence of voltage on the current-carrying parts of electrical installations.
2. General technical requirements for voltage meters are set out in the state standard.
Voltage indicators above 1000V
Principle of operation and design
3. Voltage indicators above 1000 V react to the capacitive current flowing through the indicator when its working part is introduced into the electric field formed by the current-carrying parts of electrical installations that are energized, and the "ground" and grounded structures of electrical installations.
4. Pointers must contain the main parts: working, indicator, insulating, as well as a handle.
5. Working part contains elements that react to the presence of voltage on the controlled current-carrying parts.
The working part may contain a tip electrode for direct contact with controlled current-carrying parts and not contain a tip electrode (non-contact pointers).
indicator part, which can be combined with the working one, contains elements of light or combined (light and sound) indication. Luminous and sound signals must be reliably recognizable.
The working part may also contain an organ of its own control of serviceability. Control can be carried out by pressing a button or be automatic, by periodically supplying special control signals.
6. The insulating part can be a composite of several links. To connect the links to each other, parts made of metal or insulating material can be used. The use of a telescopic design is allowed, while spontaneous folding should be excluded.
7. The handle can be one piece with the insulating part or be a separate link.
8. The design and weight of the signs must ensure the possibility of working with them by one person.
9. Wiring diagram and the design of the pointer must ensure its operability without grounding the working part of the pointer, including when checking the absence of voltage, carried out from telescopic towers or from wooden and reinforced concrete poles of 6-10 kV overhead lines.
10. The indication voltage of the voltage indicator should be no more than 25% rated voltage electrical installations.
11. The time of appearance of the first signal after touching the current-carrying part, which is energized, equal to 90% of the rated phase, should not exceed 1.5 s.
12. The working part of the pointer to a certain voltage should not react to the influence of neighboring circuits of the same voltage.
Performance tests
13. During operation, mechanical tests of voltage indicators are not carried out.
14. Electrical Tests voltage indicators consist of testing the insulating part with increased voltage and determining the indication voltage.
For voltage meters with a built-in power source, its condition is monitored and, if necessary, the batteries are recharged or the batteries are replaced.
15. When testing the insulation of the working part, the voltage is applied between the tip electrode and the screw connector or at the border of the working part.
16. When testing the insulating part, voltage is applied between the element of its articulation with the working part (threaded element, connector, etc.) and a temporary electrode applied at the restrictive ring from the side of the insulating part.
17. The indicator voltage is checked as follows - the voltage of the test set rises smoothly from zero to a value at which the light signals begin to correspond to 25%.
18. The rates and frequency of electrical testing of pointers are given in the table.
Terms of use
19. Before starting work with the pointer, it is necessary to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
20. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that although some types of voltage indicators can signal the presence of voltage at a distance from live parts, direct contact with them the working part of the pointer is mandatory.
21. In electrical installations with voltages above 1000V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000V
Purpose, principle of operation and design
22. In electrical installations with voltage up to 1000V, two types of indicators are used: two-pole and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole pointers operating with the flow of capacitive current, designed for electrical installations only alternating current .
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
23. Two-pole pointers consist of two cases made of electrically insulating material containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
24. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
26. Voltage indicators up to 1000V can also perform additional functions: integrity check electrical circuits, phase wire detection, polarity detection in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Extension functionality indicator should not reduce the safety of operations to determine the presence or absence of voltage.
Performance tests
27. Electrical tests of voltage indicators up to 1000 V consist of testing the insulation, determining the indication voltage, checking the operation of the indicator at an increased test voltage, checking the current flowing through the indicator at the highest operating voltage of the indicator.
If necessary, the indication voltage in the DC circuits is also checked, as well as the correctness of the polarity indication.
The voltage gradually increases from zero, while the values of the indication voltage and the current flowing through the pointer at the highest operating voltage of the pointer are fixed, after which the pointer is switched off for 1 min. maintained at an increased test voltage exceeding the highest operating voltage of the indicator by 10%.
28. When testing pointers (except for insulation testing), the voltage from the test facility is applied between the tip electrodes (for bipolar pointers) or between the tip electrode and the electrode on the end or side of the housing (for single-pole pointers).
29. When testing the insulation of two-pole indicators, both cases are wrapped in foil, and the connecting wire is lowered into a vessel with water at a temperature of (25 +/- 15) ° C so that the water covers the wire, not reaching the handles of the cases by 8 - 12 mm. One wire from the test setup is connected to the tip electrodes, the second, grounded, to the foil and lowered into the water.
For single-pole pointers, the case is wrapped with foil along the entire length to the limit stop. A gap of at least 10 mm is left between the foil and the contact on the end (side) part of the housing. One wire from the test set is connected to the tip electrode, the other to the foil.
30. The norms and frequency of operational tests of pointers are given in the table.
Terms of use
31. Before starting work with the pointer, it is necessary to check its serviceability by briefly touching live parts that are obviously energized.
32. When checking the absence of voltage, the time of direct contact of the indicator with the controlled current-carrying parts must be at least 5 s.
33. When using single-pole indicators, contact must be ensured between the electrode on the end (side) part of the body and the operator's hand. The use of dielectric gloves is not allowed.
2.4.20. Before you start working with the pointer, you need to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
The serviceability of pointers with a built-in control unit is checked in accordance with the operating manuals.
2.4.21. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that, although some types of voltage indicators can signal the presence of voltage at a distance from current-carrying parts, direct contact with them by the working part of the indicator is mandatory.
2.4.22. In electrical installations with voltages above 1000 V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000 V Purpose, principle of operation and design
2.4.23. General technical requirements for voltage indicators up to 1000 V are set out in the state standard.
2.4.24. In electrical installations with voltages up to 1000 V, two types of indicators are used: bipolar and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole indicators operating with the flow of capacitive current are intended for electrical installations only with alternating current.
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
2.4.25. Two-pole pointers consist of two cases made of electrical insulating material, containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
2.4.26. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
Indication of the presence of voltage can be stepped, given in the form digital signal etc.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
For pointers with a pulse signal, the indication voltage is the voltage at which the interval between pulses does not exceed 1.0 s.
2.4.28. Voltage indicators up to 1000 V can also perform additional functions: checking the integrity of electrical circuits, determining the phase wire, determining the polarity in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Expanding the functionality of the pointer should not reduce the safety of operations to determine the presence or absence of voltage.
Repair of electrical networks is a work related to electricity. There is always a risk of injury to the worker by current of different voltage. How do you know if current is flowing through a wire or cable strands? The voltage indicator (UN) will help determine which wire is energized. Disabling the section under the potential difference does not mean that it is absent on the current-carrying parts. Only with the help of such devices can you be sure that it does not exist.
Device and principle of operation
The main structural elements that make up any indicator are:
- one or two metal tips, the tip of which directly touches the bare current-carrying part to establish the presence or absence of voltage;
- light, sound or digital indicator, giving a signal in the presence of electricity;
- housing made of insulating material, which contains a neon light bulb, LED or led matrix, and an electronic board and a quenching resistor may also be present.
The principle of operation and the design of the pointers depend on what current will flow: active or capacitive. The first type of UN implies operation with both alternating and direct currents up to 1000 V. The second type is designed to work only with alternating currents.
Attention! An incandescent lamp with leads attached to it to control the voltage on the wires is not an indicator. Its use is strictly prohibited.
Structurally, the indicators can have two cases with tips connected to each other by a conductor. In this case, the length of such a conductor should not exceed 1 m, the places where it enters the housings (handles) are framed with a thickening and have shock-absorbing inserts.
Types of pointers for determining voltage
Conductive parts of installations with which electrical personnel have to work are divided according to the magnitude of the supply voltage. There are circuits with voltages up to 1000 V and over 1000 V. Due to the fact that the use of UN involves touching it with a working electrode to a bare wire, indicators are divided into voltage indicators up to 1000 V and those designed for voltages above 1000 V.
In addition, UN are divided according to the following characteristics:
- the number of poles (with one or two contact electrodes);
- type of current (direct or alternating);
- indicator type (neon, LED, digital, acoustic).
In the line of modern indicators, there are samples with non-contact testing for the presence of high voltage. UN allows you to check the presence of Uph (Uf) on high-voltage lines (VL) and busbar current assemblies of closed (ZRU) and open (ORG) switchgear with Uf from 1 kV and higher.
Information. The non-contact UN produces an intermittent optical or acoustic signal when its testing part approaches the element under Uf. Own power supply allows not only to issue indication signals, but also to control the health of the UN.
Single pole pointer
Low voltage indicators (UNN) with one pole have a neon bulb located in the housing. It has an ignition threshold of up to 90 V and a series-connected resistance, one end of which is connected to the contact pad on the indicator housing. To determine the presence of Uf, it is necessary to touch the bare wire with the pointer tip, and with your finger - the contact pad on the case. As a result, the capacitive circuit closes through the human body to the ground. When voltage is present, the indicator lights up.
Single-pole pointers can be made in the form of a screwdriver with a transparent case, inside which a light bulb glows. Examples of such probes are INO-70, UNN-90 and others.
Carefully. Single-pole indicators are designed to test the absence or presence only AC voltage. Before use, it is necessary to know the value of the maximum permissible potential difference. This information is printed on the body of the device.
Bipolar voltage indicator
Voltage indicators pin 90 refer to the UN, having two poles of connection to the section that conducts electric current. Pin 90, as a model representing such testers, allows you to work in the range of values from 50 V to 1000 V. It is permissible for them to determine the presence of a “phase” by the glow of the lamp, touching one electrode to the test area, the other to the neutral or ground conductor. In the absence of such, the presence of phase voltage can be determined by touching one contact tip to the “phase”, the other by touching the finger of the hand. In three-phase AC networks, both phase (220 V) and line voltage (380 V) can be checked.
Important! Before working with UN, it is necessary to visually inspect the housings for the absence of mechanical damage, flexible conductor - on the integrity of the insulation. Before work, you must make sure that the indicator is working by touching the area that is obviously under voltage.
High voltage indicators (UVN) over 1 kV
On power lines 6-10 kV, a voltage indicator uvn 10 is used. This device allows you to control Uph, both on overhead lines and in high-voltage ground installations. It belongs to the group of basic protective equipment for work in the EU, since with its help it is necessary to touch the live parts of the installations.
The device includes: a working part, an insulating section and a handle. In the working part there is an electrical circuit that converts an electrical signal into a light and sound form. The circuit is located in the shader (reflector) area, which is designed to enhance optical and acoustic indications. This is achieved through its directed action.
The main requirements for the design of UVN:
- indication signals must have a continuous or intermittent mode of operation and be clearly recognizable;
- the insulating part must be located strictly between the handle and the working part;
- if the insulating part consists of several links (collapsible) or telescopic, then the fastening between the links must ensure the strength of the entire structure, sliding fixation from spontaneous movement;
- the pointer must have a mass that allows one person to work with it;
- the rubber or plastic casing of the shader must contain a mirror reflector.
Such indicators should have a design that allows testing the voltage on a 6 kV or 10 kV overhead line without grounding their working parts.
Universal Pointers
The instruction-scheme of such devices describes them as a portable tester that allows sound and light indication during testing. It is used to determine:
- phase;
- zero;
- absence or presence of voltage (from 12 to 500 V DC and up to 380 V AC).
With the help of such UN, it is possible to carry out a "diagnosis" of the integrity of the circuit and find out the order of alternation or phase coincidence. The power source in the universal probe is a capacitor with a large capacitance value. It can be equipped with a line of LEDs or a liquid crystal display.
One of the representatives of the universal UN models is “contact 55 em”. It has the following options:
- operating voltage range - 24-380 V DC or AC;
- electrical insulation strength - 1 kV;
- current through the pointer at 380 V - up to 10 mA;
- Rmax of the external circuit during continuity - at least 500 kOhm.
Such a device can work without recharging for 24 hours, the charge time is no more than 30 seconds.
The control of the presence or absence of voltage is carried out by light and sound indication. The ability to mount a second probe on the body of the first allows you to easily test the power off at the outlet.
Design and method of application
The product manual describes design features and operating rules. Typical recommendations may have some discrepancy with individual developments. However, the basic requirements are met for all models:
- ferrule;
- dielectric housing;
- display device.
During operation, it is necessary to touch the test area, taking into account what voltage may be present there, and whether it falls within the operating range of the indicator.
Important! If there are no assumptions under what voltage the de-energized section may be, the lack of potential is checked first by the UVN, then the UNN.
Bipolar voltage indicator
To the sizes of two-pole indicators there are no certain requirements. The main thing is that they fit comfortably in the hand, the length of the conductor located between the handles made it possible to reach closely located sections of the current leads. The indicator of even such simple devices as a 90 m pin should not mislead the operator about the test results. Tips (electrodes) must be fixed firmly, their size should not exceed 7 mm.
High voltage device (more than 1 kV)
Such devices can be both single-pole and two-pole: UVN - 10, UVN - 80 and similar models. For example, you can consider a high voltage indicator uvn 10.
With its help, the phasing of power transformers in the power plant and cables designed for operation from alternating current with a frequency of f = 50 - 60 Hz and U = 6 - 10 kV is carried out.
There are several versions of this device, which have:
- impulse light indication with self-control (UVNU -10 SZ);
- the same parameters plus power supply (UVNU - 10 SZ IP);
- phase indicator, light-pulse indication plus phasing tube, IP is absent (UVNU - 30 SZ TF);
- the same parameters as the previous model, plus IP (UVNU - 10 SZ IP TF);
- UN with IP contact-non-contact (UVNU - 10 SZ IP KB);
- indication of phases, power supply, phasing tube, bipolar (UVNU - 10 SZ IP KB TF).
Despite the abundance of indicators designed for different voltages and types of current, all of them must be periodically tested in special laboratories.
Pointer tests
Laboratory tests are carried out by organizations that have a special license for this. To carry out the test, a circuit is assembled in which a high or low voltage indicator is included.
UNN is tested for the state of insulation, the magnitude of the voltage indication. They also check its operation at increased voltage, while measuring the current. Gradually enlarged from zero value the voltage is brought to exceed the working voltage by 10% and maintained for 1 min.
UVN is tested starting from the working part, applying voltage to the tip and screw connection. If the indicator voltage is higher than 35 kV, the working part is not checked, only the condition of the insulating part and the handle are tested.
The results obtained are documented and logged. A tag with a stamp is installed on the product approved for use, where the date of the next verification is indicated.
Voltage gauges and indicators serve to ensure the safety of maintenance personnel during work, they can also be fraught with danger. Storage, proper use and daily visual inspection should be provided to those who directly use the pointer. It is forbidden to use the device if the test period has expired, as well as if it has been subjected to mechanical stress as a result of a fall or impact.
Video
Purpose
2.4.1. Voltage indicators are designed to determine the presence or absence of voltage on the current-carrying parts of electrical installations.
2.4.2. General technical requirements for voltage meters are set out in the state standard.
Voltage indicators above 1000 V
Principle of operation and design
2.4.3. Voltage indicators above 1000 V react to the capacitive current flowing through the indicator when its working part is introduced into the electric field formed by the current-carrying parts of electrical installations that are energized, and the "ground" and grounded structures of electrical installations.
2.4.4. Pointers should contain the main parts: working, indicator, insulating, as well as a handle.
2.4.5. The working part contains elements that respond to the presence of voltage on the controlled current-carrying parts.
Cases of working parts of voltage indicators up to 20 kV inclusive must be made of electrically insulating materials with stable dielectric characteristics. Cases of working parts of voltage indicators of 35 kV and above can be made of metal.
The working part may contain a tip electrode for direct contact with controlled current-carrying parts and not contain a tip electrode (non-contact pointers).
The indicator part, which can be combined with the working part, contains elements of light or combined (light and sound) indication. Gas-discharge lamps, light-emitting diodes or other indicators can be used as elements of light indication. Light and sound signals must be reliably recognizable. The audio signal should have a frequency of 1 - 4 kHz and an interruption frequency of 2 - 4 Hz when indicating phase voltage. The sound signal level must be at least 70 dB at a distance of 1 m along the axis of the sound emitter.
The working part may also contain an organ of its own control of serviceability. Control can be carried out by pressing a button or be automatic, by periodically supplying special control signals. At the same time, it should be possible to fully check the serviceability of the electrical circuits of the working and indicator parts.
Working parts should not contain switching elements designed to turn on power or switch ranges.
2.4.6. The insulating part of the pointers must be made of the materials specified in clause 2.1.2.
The insulating part may be composed of several links. To connect the links to each other, parts made of metal or insulating material can be used. The use of a telescopic design is allowed, while spontaneous folding should be excluded.
2.4.7. The handle can be one piece with the insulating part or be a separate link.
2.4.8. The design and weight of the pointers should ensure that one person can work with them.
2.4.9. The electrical circuit and design of the pointer must ensure its operability without grounding the working part of the pointer, including when checking the absence of voltage, carried out from telescopic towers or from wooden and reinforced concrete supports of 6-10 kV overhead lines.
2.4.10. The minimum dimensions of the insulating parts and handles of voltage indicators above 1000 V are given in Table. 2.4.
Table 2.4
MINIMUM DIMENSIONS OF INSULATING PARTS AND HANDLES OF VOLTAGE INDICATORS ABOVE 1000 V
2.4.11. The indication voltage of the voltage indicator should not exceed 25% of the rated voltage of the electrical installation.
For pointers without a built-in power supply with a pulse signal, the indication voltage is the voltage at which the signal interruption frequency is at least 0.7 Hz.
For pointers with a built-in power supply with a pulse signal, the indication voltage is the voltage at which the signal interruption frequency is at least 1 Hz.
For other indicators, the indication voltage is the voltage at which there are distinct light (light and sound) signals.
2.4.12. The time of appearance of the first signal after touching the current-carrying part under voltage equal to 90% of the rated phase voltage should not exceed 1.5 s.
2.4.13. The working part of the indicator for a certain voltage should not respond to the influence of neighboring circuits of the same voltage, spaced from the working part at the distances indicated in Table. 2.5.
Table 2.5
DISTANCE TO THE NEAREST WIRE OF THE ADJACENT CIRCUIT
Performance tests
2.4.14. During operation, mechanical tests of voltage indicators are not carried out.
2.4.15. Electrical tests of voltage indicators consist of testing the insulating part with increased voltage and determining the indication voltage.
The test of the working part of voltage indicators up to 35 kV is carried out for indicators of such a design, during operations with which the working part can cause an interphase short circuit or a phase-to-ground short circuit. The need to test the insulation of the working part is determined by the operating manuals.
For voltage meters with a built-in power source, its condition is monitored and, if necessary, the batteries are recharged or the batteries are replaced.
2.4.16. When testing the insulation of the working part, voltage is applied between the tip electrode and the screw connector. If the pointer does not have a screw connector electrically connected to the indication elements, then the auxiliary electrode for connecting the wire of the test setup is installed at the boundary of the working part.
2.4.17. When testing the insulating part, voltage is applied between the element of its articulation with the working part (threaded element, connector, etc.) and a temporary electrode applied at the restrictive ring from the side of the insulating part.
2.4.18. The indication voltage of indicators with a gas-discharge indicator lamp is determined according to the same scheme by which the insulation of the working part is tested (clause 2.4.16).
When determining the indication voltage of other indicators with a tip electrode, it is connected to the high-voltage output of the test facility. When determining the indication voltage of pointers without a tip electrode, it is necessary to touch the end side of the working part (head) of the pointer to the high-voltage output of the test setup.
In both latter cases, the auxiliary electrode is not installed on the indicator and the ground terminal of the test set is not connected.
The voltage of the test setup smoothly rises from zero to the value at which the light signals begin to comply with the requirements of clause 2.4.11.
2.4.19. The norms and frequency of electrical testing of pointers are given in Appendix 7.
Terms of use
2.4.20. Before you start working with the pointer, you need to check its serviceability.
The serviceability of pointers that do not have a built-in control body is checked using special devices, which are small-sized sources of increased voltage, or by briefly touching the pointer tip electrode to live parts that are obviously energized.
The serviceability of pointers with a built-in control unit is checked in accordance with the operating manuals.
2.4.21. When checking the absence of voltage, the time of direct contact of the working part of the indicator with the controlled current-carrying part must be at least 5 s (in the absence of a signal).
It should be remembered that, although some types of voltage indicators can signal the presence of voltage at a distance from current-carrying parts, direct contact with them by the working part of the indicator is mandatory.
2.4.22. In electrical installations with voltages above 1000 V, the voltage indicator should be used with dielectric gloves.
Voltage indicators up to 1000 V
Purpose, principle of operation and design
2.4.23. General technical requirements for voltage indicators up to 1000 V are set out in the state standard.
2.4.24. In electrical installations with voltages up to 1000 V, two types of indicators are used: bipolar and single-pole.
Two-pole indicators operating with the flow of active current are designed for electrical installations of alternating and direct current.
Single-pole indicators operating with the flow of capacitive current are intended for electrical installations only with alternating current.
The use of two-pole pointers is preferred.
The use of test lamps to check the absence of voltage is not allowed.
2.4.25. Two-pole pointers consist of two cases made of electrical insulating material, containing elements that respond to the presence of voltage on the controlled current-carrying parts, and elements of light and (or) sound indication. The housings are interconnected by a flexible wire with a length of at least 1 m. In the places of inputs into the housings, the connecting wire must have shock-absorbing bushings or thickened insulation.
The dimensions of the cases are not standardized, they are determined by ease of use.
Each case of a two-pole pointer must have a rigidly fixed tip electrode, the length of the uninsulated part of which should not exceed 7 mm, except for pointers for overhead lines, in which the length of the uninsulated part of the tip electrodes is determined by the technical specifications.
2.4.26. A single-pole pointer has one housing made of electrically insulating material, in which all the elements of the pointer are placed. In addition to the tip electrode that meets the requirements of clause 2.4.25, there must be an electrode on the end or side of the body for contact with the operator's hand.
The dimensions of the case are not standardized, they are determined by ease of use.
The indication of the presence of voltage can be stepped, supplied in the form of a digital signal, etc.
Light and sound signals may be continuous or intermittent and must be reliably recognizable.
For pointers with a pulse signal, the indication voltage is the voltage at which the interval between pulses does not exceed 1.0 s.
2.4.28. Voltage indicators up to 1000 V can also perform additional functions: checking the integrity of electrical circuits, determining the phase wire, determining the polarity in DC circuits, etc. At the same time, the indicators should not contain switching elements intended for switching operating modes.
Expanding the functionality of the pointer should not reduce the safety of operations to determine the presence or absence of voltage.
Performance tests
2.4.29. Electrical tests of voltage indicators up to 1000 V consist of testing the insulation, determining the indication voltage, checking the operation of the indicator at an increased test voltage, checking the current flowing through the indicator at the highest operating voltage of the indicator.
If necessary, the indication voltage in the DC circuits is also checked, as well as the correctness of the polarity indication.
The voltage gradually increases from zero, while the values of the indication voltage and the current flowing through the pointer at the highest operating voltage of the pointer are fixed, after which the pointer is switched off for 1 min. maintained at an increased test voltage exceeding the highest operating voltage of the indicator by 10%.
2.4.30. When testing indicators (except for insulation testing), the voltage from the test apparatus is applied between the tip electrodes (for bipolar indicators) or between the tip electrode and the electrode on the end or side of the housing (for single-pole indicators).
Rice. 2.1. circuit diagram testing the dielectric strength of the insulation of the handles and the wire of the voltage indicator:
1 - test pointer; 2 - test transformer; 3 - bath with water; 4 - electrode
2.4.31. When testing the insulation of two-pole indicators, both cases are wrapped in foil, and the connecting wire is lowered into a vessel with water at a temperature of (25 +/- 15) ° C so that the water covers the wire, not reaching the handles of the cases by 8 - 12 mm. One wire from the test setup is connected to the tip electrodes, the second, grounded, to the foil and lowered into the water (diagram variant - Fig. 2.1).
For single-pole pointers, the case is wrapped with foil along the entire length to the limit stop. A gap of at least 10 mm is left between the foil and the contact on the end (side) part of the housing. One wire from the test set is connected to the tip electrode, the other to the foil.